In the construction of undercarriages intended for different machines, the variation in gauge is achieved by forming the structure of the undercarriage with telescopic cross-beams actuated by suitable hydraulic means. Known solutions fall within two typical arrangements.
A first frequently-used arrangement, provides for the telescoping of the cross-beams, which enables the tracks of the undercarriage to be moved towards or away from each other independently by means of hydraulic cylinders located outside the cross-beams themselves. In this case the telescoping of the cross-beams takes place in a staggered manner on the corresponding sides of the undercarriage, resulting in structural imbalances which, because of the irregular distribution of the masses in question, affects the stability of the entire carriage with unacceptable consequences in certain applications such as lifting machines, for example, track laying cranes.
In this arrangement, the operations of narrowing or widening the gauge are normally carried out manually and, in any case, the travel limit and adjusting devices are operated manually or by interlocked controls without valves and without any guarantee of the locking of the movable parts of the structure in the fully-extended working positions.
A second arrangement, designed specifically for application to so-called mechanically integrated lifting devices provides cylinders for controlling the variable gauge to operate within the telescopic cross-beams connecting the tracks. This arrangement is characterised by the engagement of locking pins for ensuring that there are no geometric variations in the gauge of the undercarriage during working, which is manual both in terms of control and engagement of the stops.